The invention relates to a multi-axle unit for a semi-trailer that is towed by a tractor vehicle and has at least three axles, at least one of the axles of the multi-axle unit being capable of being configured as a lifting axle and/or steered axle.
Tractor-trailer units having multi-axle units are known from German Patent Application No. 196 32 515 A1, among others. Lifting axles have previously been described in German Patent Application No. 41 14 861 A1, among others. In tractor-trailer units up to a permitted gross weight of, for example 40 tons, semi-trailers with three-axle chassis are generally used. The individual axles have single-tire wheels. In these known multi-axle units, all the wheels of the axles are generally equipped with wheel brakes. The brakes of at least two axles of the multi-axle units are equipped with accumulator brake cylinders for use as a parking brake.
The axle of a semi-trailer described in German Patent Application No. 196 32 515 A1 has one disk brake per wheel. The disk brakes used are of considerably smaller dimensions than the disk brakes of the tractor vehicle. Lastly, at least the dynamic wheel loads of the tractor vehicle are considerably greater than those of the semi-trailer, thus resulting in a lower braking force requirement there.
An object underlying the present invention is that of developing a multi-axle unit for semi-trailers that, due to a particular configuration of the braking system, has a lower unsprung mass, requires less maintenance outlay, exhibits safe driving characteristics, and moreover is more economical to manufacture, install, and maintain.
The present invention provides a multi-axle unit for a semi-trailer that is towed by a tractor vehicle and has at least three axles, at least one of the axles of the multi-axle unit being capable of being configured as a lifting axle and/or steered axle, wherein all axles of the multi-axle unit except for at least one axle are equipped with disk brakes; and the brake disks of the brakable axles of the multi-axle unit at least have the same effective frictional radius as the brake disks of the tractor vehicle. On the multi-axle unit, all axles except for at least one axle are equipped with disk brakes, the brake disks of the brakable axles of the multi-axle unit at least having the same effective frictional radius as the brake disks of the tractor vehicle.